1. Field of the Invention
The invention relates generally to distance sensors, and, more particularly, to a radar proximity sensor for missiles and projectiles.
2. Description of Related Art Including Information Disclosed Under .sctn..sctn. 1.97-1.99
(U) Radar proximity sensors using random binary phase modulation have the problem that part of the transmit signal leaks into the receiver via reflections at the antenna caused by antenna mismatch. The leakage signal is noisy due to the random noise-like modulation and is a much more powerful signal than the typical return signal reflected from a target. If the leakage sisal contains noise components which fall lute, the Doppler band, the desired signal will be desensitized.
In the past, random bit sequences have not used because of this noise problem. Only so called pseudorandom bit sequences were used, i.e., bit patterns that repeat. Then the noise contains only spectral lines that are multiples of the pattern repetition rate and can be made to fall outside the Doppler spectrum.
Unfortunately, a pseudorandom binary bit sequence: can be recovered and utilized to create interference signals to frustrate the purpose of the proximity sensor, e.g., to prefire a proximity fuze of an artilliary projectile.